Switch head construction permitting observation of contact jaws



July 16, 1963 R. R. FARRELL 3,098,142

SWITCH HEAD CONSTRUCTION PERMITTING OBSERVATION OF CONTACT JAWS Filed April 8, 1960 3 Sheets-Sheet 1 IN V EN TOR. 190,558 7 E. fflzeffll July 16, 1963 R. R. FARRELL 7 3,098,142

'swrrca HEAD CONSTRUCTION PERMITTING OBSERVATION 0F CONTACT JAWS Filed April 8, 1960 3 Sheets-Sheet 2 July 16, 1963 R. R FARRELL 3,

SWITCHHEAD CONSTRUCTION PERMITTING OBSERVATION OF CONTACT JAWS Filed April 8, 1960 a Sheets-Sheet s INVENTOR. 06156 7' e. Fflktefzl A rram yw United States Patent 3,098,142 SWITCH HEAD CONSTRUCTION PERMITTING OBSERVATION OF CONTACT JAWS Robert R. Farrell, Toronto, Ontario, Canada, assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa, a

corporation of Pennsylvania Filed Apr. 8, 1960, Ser. No. 26,927 2 Claims. (Cl. 200168) This invention relates to a switch head construction for permitting visual observation of the contact jaws when the switch is in the Ofi position, and more specifically is an improvement of the molded switch head shown in U.S. Patent No. 2,820,123 to L. W. Higgins et al., entitled Molded Switch Head, issued January 14, 1958 and assigned to the assignee of the instant invention.

Molded switch heads as described in the above noted patent are well known to the art, and are formed of a contact member which is surrounded by an insulating medium. A pair of relatively stationary contacts enter the insulating medium through a channel therein to engage the contact member or movable contact carried by the switch head. The insulating structure which carries the movable contact further includes .an insulating barrier which follows behind the movable contact when it is moved to a disengaged position. Thus, rc interruption is achieved, first, because of the interposition of the insulating barrier between the movable contact and the stationary contacts, and, secondly, because the insulating head surrounding the contacts restricts the amount of oxygen or ionizable gas to which the arc is opened.

It has always been though necessary that the substantially airtight enclosure formed by the switch head should be retained at all times so that when the movable switch is moved to the fully Off position, the stationary contacts entering the switch head are still within the head and enclosed by the skirts of the head, so that the tips of the stationary contacts are not observable. However, it is often highly desirable that visual inspection of the condition of the tips of the stationary contacts be inspected.

It has been found that the skirts covering the stationary contact portion after the switch head has been moved to its Oif position can be cut back so that the contact tips of the stationary contacts can be observed without impairing the operation of the contacting device. That is to say, the substantially airtight seal formed between the skirts of the switch head and the stationary contact jaws may be defeated after the switch head has been moved a predetermined distance toward the Off position. At this predetermined point, the arc has already been extinguished by the effect of the insulating barrier and the airtight seal prior to the time that skirts leave the contact jaws.

By cutting back the skirts, it is apparent that the contact jaws will now be subject to visual observation.

As a second embodiment of the invention, it has been found that the complete switch head or portions thereof which are adjacent the contact jaws can be made of a transparent insulating material which may be a thermo-setting or thermo-plastic moldable compound. One such compound which has been found to be useful is the therm-o-plastic polycarbon sold under the trade name of Lexan, a registered trademark owned by the General Electric Company.

Accordingly, .a primary object of this invention is to provide a molded switch head which permits visual observation of the contact jaws.

Another object of this invention is to provide visual observation of the stationary contact jaws cooperating with a molded switch head when the molded switch head is moved to an Off position.

3,098,142 Patented July 16, 1963 A further object of this invention is to cut back the skirts of a molded switch head so that the stationary contact jaws cooperating with the switch head will be exposed for visual observation when the switch head is moved to its 01f position without interfering substantially with the operation of the switch.

A still further object of this invention is to provide a switch head having at least a partial transparent portion therein of insulating material which permits visual observation of the stationary contact jaws.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 shows an exploded perspective view of a molded switch head constructed in accordance with the present invention.

FIGURE 2 shows a perspective interior view of one of the telescoping portions of the switch head of FIG- URE 1.

FIGURE 3 shows a side plan view of the assembled switch head of FIGURE 1.

FIGURE 4 shows a side cross-sectional view of the switch head of FIGURES 1 and 3 with the switch head in an On position.

FIGURE 5 shows the switch head of FIGURE 4 in cross-section, and in the Off position.

FIGURE 6 shows a cross-sectional view of FIGURE 4 along the lines 66 of FIGURE 4, and particularly illustrates the manner in which the two halves of the molded switch head telescope with respect to one another.

FIGURE 7 shows a cross-sectional view of FIGURE 5 taken across the lines 7-7 of FIGURE 5 to particularly show the manner in which the contact slug land biasing spring are assembled within the switch head.

FIGURE 8 is a side plan view of the switch head of FIGURE 5 in the disengaged position, and particularly illustrates the manner in which the stationary contact jaws are rendered visible because of the cut-away skirt portion of the switch head.

FIGURE 9 illustrates a three-phase circuit interrupter contained in a housing enclosure where each of the phases includes a switch head of the type shown in the preceding figures.

FIGURE 10 is a side view of the assembled interrupter of FIGURE 9 with portions thereof cut away for illustrating the position of the switch heads.

FIGURE 11 shows a second embodiment of the invention wherein the skirt portions of the switch head are not cut away, but are of a transparent insulating material to permit visual observation.

Referring now to the figures, the embodiment shows the type of switch head shown in above noted Patent 2,820,123, the exception being that the lower skirts of the switch head are cut away in part in accordance with the present invention. More particularly, the molded switch head is formed of two insulating sections 1t and 12 which telescope with respect to one another, as shown in FIG- URES 1 and 6.

The internal portions of telescoping sections 10 and 12, as shown in FIGURES 1, 2, 6 and 7, are molded to provide means for seating movable contact slug 14 and a biasing spring 16 which surrounds contact slug 14, as shown in FIGURES 4, 5 and 7.

An insulating barrier 18 of FIGURES '1, 3, 5 and 7 is molded integral with switch head portion 10, and is positioned immediately below movable contact slug 14 for purposes to be described hereinafter.

In order to move the switch head between an On and OE position, and to further rigidly maintain telescoping portions 10 and 12 assembled, a bale 20 is provided which has extending ears 22 and 24 which cooperate with molded extensions 26 switch head portions 12 and 10 respectively, as best seen in FIGURES 1 and 6. Thus, the bale holds the assembled unit together. Further to this, however, the bale extends upwardly to form an operating portion 30 which can receive an operating bar, such as bar 32 of FIGURES 3, 4, 5 and 7, and as will be more fully described hereinafter.

In accordance with the present invention, the skirt portions or walls 33 and 34- of head portion 10 do not extend completely downwardly so that they will surround the stationary contact jaws when the switch head is moved to an Off position. This may be understood with reference to FIGURES 4 and 5 which show the switch head in an On and Off position respectively with respect to contact jaws 36 and 38. Thus, in FIGURE 4, when the switch head is in the On position, it will be seen that the switch head is depressed so that the contact jaws 36 and 38 extend upwardly and into engagement on either side of contact slug 14 with biasing spring 16 biasing the contact jaws toward this engagement.

It will be noted in FIGURE 4 that a substantial airtight seal is formed in the volume occupied by contact slug 14 by virtue of the stationary contact members 36 and 38 entering the channels formed in the switch head. In the past, when the switch head was moved to the Off position, it was felt necessary that the tips of the contact jaws be retained in these channels to always seal off this small volume. It has been found, however, that this volume need not be sealed after substantial are interruption occurs, and that, in fact, this seal may be defeated after arc interruption which occurs after a relatively short motion of the switch head to the Off position.

In accordance with the present invention, and following this observation, the lower skirt portions of the switch head are cut back so that, as shown in FIGURE 5, the skirt portions 32 and 34 will clear the ends of stationary contacts 36 and 38 when the switch head is moved to its OII' position. Since these skirt portions clear the movable contacts, visual observation of the contacts will now be possible, as shown in FIGURE 8 which shows a side plan view of FIGURE 5, and clearly illustrates how the foreshortened skirt 32 exposes the contact tip of contact 38. In a like manner, the foreshortened skirt 34 will expose contact 36 to visual observation from the opposite side of the switch head.

The manner in which the switch heads are assembled in an operating unit is illustrated in FIGURES 9 and 10 for the case of a multiphase unit. FIGURES 9 and 10 show a housing 40'having a door 42 hinged thereto which is movable between the closed position of FIGURE to the'open position of FIGURE 9. A base of insulating material 44 is secured to the bottom of housing 40 and receives a first set of terminals 46, 48 and 50 which may have the form of an L-shape, and serve the purpose of one of the contact jaws, such as contact jaws 36 or 38 of FIGURES 4 and for respective switch heads 52, 54 and 5 6.

The second stationary contact for switch heads 52, 54 and 56 is then shown as conductor elements having terminals 58, 60 and 62. Thus, terminals 46, 4'8 and 50' and terminals 58, 60 and 62 are electrically connected to staand 28 respectively of tionary contacts of the type shown in FIGURES 4 and 5 as stationary contacts 36 and 38 for receiving respective switch heads.

A second set of terminals 64, 66 and 68 for each of the respective phases of the interrupter of FIGURES 9 and are then provided which are adapted to receive plug-in fuses (not shown) which are to be connected in series with a respective switch head. The terminals 46, 48 and 50 may then receive electrical connections brought into box 40 through knock-out 70 while terminals 64, 66 and 68 may be connected to cables from the load being controlled by the switch, for example, to a neutral bar assembly 72. The neutral bar assembly 72' permits the complete load connection to be made. In order to operate the switch heads 52, 54 and 56 of FIGURE 9 between the On position of FIGURE 4 to the Off position of FIGURE 5, the operating rod 32 (FIGURES 4 and 5) is provided with one end pivoted at pivot 74 and its other end connected to an operating handle 76. When the operating handle 76 is rotated upwardly to bring the switch heads to their Off position (shown in FIGURES 9 and 10), in accordance with the present invention, the skirts of the switch heads are shortened, and the OE position raised to a higher position than previously attained, whereby the ends of contacts 36 and 38 are made visible from either side of box 40. Conversely, the skirts can be considerably foreshortened whereby the switch may be installed in presently existing equipment, and still render the stationary contacts visible when the switch heads are in the Off position.

In an alternative embodiment of the present invention, and as is specifically illustrated in FIGURE 11, the skirts of the switch, such as skirt 32 may have the same length as was previously used whereby the stationary contacts, such as contacts 36 and 38, will always be within the contact passages provided in the molded switch head so that the interior of the switch head is always enclosed. In order, however, to provide visibility of the contact ends, a transparent insert 78 is provided at the bottom of the skirt which serves as a window, for example, for contact 38. This transparent insert is of an insulating material, such as a thermoplastic polycarbon, and may be of any presently available transparent thermo-setting or thermoplastic moldable compound.

Although this invention has been described with respect to its preferred embodiments it should be understood that [many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of this invention be limited not by the specific disclosure herein but only by the appended claims.

What is claimed is:

1. In a molded switch head; said molded switch head having an internal chamber; said internal chamber having a first contact element mounted therein; said molded switch head having an elongated skirt defining a channel extending from said internal chamber to an area external of said molded switch head; a second contact element; means mounting said second contact element adjacent said molded switch head, whereby the end of said second contact element is adapted to enter said internal chamber through said channel to engage said first contact element; said molded switch head and said second contact element being movable with respect to one another between an engaged and disengaged position whereby said first and second contact elements are engaged in said engaged position and disengaged in said disengaged position; at least said end portion of said second contact element located within the volume defined by said molded switch head at said engaged and disengaged position; said end positioned within said internal chamber corresponding to said engaged position; said end positioned within said channel corresponding to said disengaged position, and located a predetermined distance from said first contact element; said elongated skirt clearing the end of said second contact element when said molded switch head is in said disengaged position with respect to said second contact element whereby said end of said second contact element is exposed for visual inspection; said channel including barrier means operatively positioned adjacent said second contact element to guide the movement between said disengaged and engaged positions.

2. In a molded switch head; said molded switch head having an internal chamber; said internal chamber having a contact slug mounted therein; said internal chamber having an insulation member extending from the bottom of said contact slug to an area external of said molded switch head; said molded switch head having a skirt member surrounding said insulation member and defining a first and second channel on either side of said insulation member respectively extending from said internal chamber to said area external of said molded switch head; a first and second contact member; means mounting said first and second contact members adjacent said molded switch head, whereby the ends of said first and second contact members are adapted to enter said internal chamber thnongh said first and second channels respectively; said molded switch head and said first and second contact members being relatively movable between an engaged and disengaged position; said contact slug engaging said first and second contact members when said molded switch head is in said engaged position; at least said end portions of said first and second contact members locate-d within the volume defined by said molded switch head at said engaged and disengaged positions; said ends positioned within said internal cham ber corresponding to said engaged position; said ends positioned Within said first and second channels corresponding to said disengaged position, and located a predetermined distance from said contact slug; said elongated skint clearing the ends of said first and second contact members when said molded switch head is in said disengaged position whereby said ends of said first and second contact members are exposed for visual observation; said channels including barrier means operat-ively positioned adjacent said second contact member to guide the movement between said disengaged and engaged positions.

References Cited in the file of this patent UNITED STATES PATENTS 2,323,476 Lantz July 6, 1943 2,491,272 Knapp Dec. 13, 1949 2,668,891 Driescher Feb. 9, 1954 2,820,123 Higgins et al. Ian. 14, 1956 2,820,866 Graybill et a1. Jan. 21, 1958 2,866,964 Neidenberg et a1 Dec. 30, 1958 

2. IN A MOLDED SWITCH HEAD; SAID MOLDED SWITCH HEAD HAVING AN INTERNAL CHAMBER; SAID INTERNAL CHAMBER HAVING A CONTACT SLUG MOUNTED THEREIN; SAID INTERNAL CHAMBER HAVING AN INSULATION MEMBER EXTENDING FROM THE BOTTOM OF SAID CONTACTS SLUG TO AN AREA EXTERNAL OF SAID MOLDED SWITCH HEAD; SAID MOLDED SWITCH HEAD HAVING A SKIRT MEMBER SURROUNDING SAID CHANNEL ON EITHER SAID OF SAID INING A FIRST AND SECOND CHANNEL ON EITHER SAID OF SAID INSULATION MEMBER RESPECTIVELY EXTENDING FROM SAID INTERNAL CHAMBER OF SAID AREA EXTERNAL OF SAID MOLDED SWITCH HEAD; A FIRST AND SECOND CONTACT MEMBER; MEANS MOUNTING SAID FIRST AND SECOND CONTACT MEMBERS ADJACENT SAID MOLDED SWITCH HEAD, WHEREBY THE ENDS OF SAID FIRST AND SECOND CONTACT MEMBERS ARE ADAPTED TO ENTER SAID INTERNAL CHAMBER THROUGH SAID FIRST AND SECOND CHANNELS RESPECTIVELY; SAID MOLDED SWITCH HEAD AND SAID FIRST AND SECOND CONTACT MEMBERS BEING RELATIVELY MOVABLE BETWEEN AN ENGAGED AND DISENGAGED POSITION; SAID CONTACT SLUG ENGAGING SAID FIRST AND SEDOND CONTACT MEMBERS WHEN SAID MOLDED SWITCH HEAD IS IN SAID ENGAGED POSITION; AT LEAST SAID END PORTIONS OF SAID FIRST AND SECOND CONTACT MEMBERS LOCATED WITHIN THE VOLUME DEFINED BY SAID MOLDED SWITCH HEAD AT SAID ENGAGED AND DISENGAGED POSITIONS; SAID ENDS POSITIONED WITHIN SAID INTERNAL CHAM-ERBER CORRESPONDING TO SAID ENGAGED POSITION; SAID ENDS POSITIONED WITHIN SAID FIRST AND SECOND CHANNLS CORRESPONDING TO SAID DISENGAGED POSITION, AND LOCATED A PREDETERMINED DISTANCE FROM SAID FIRST AND SECOND CONTACT SKIRT CLEARING THE ENDS OF SAID FIRST AND SECOND CONTACT MEMBERS WHEN SAID MOLDED SWITCH HEAD IS IN SAID DISENGAGED POSITION WHEREBY SAID ENDS OF SAID FIRST AND SECOND CONTACT MEMBERS ARE EXPOSED FOR VISUAL OBSERVATION; SAID CHANNELS INCLUDING BARRIER MEANS OPERATIVELY POSITIONED ADJACENT SAID SECOND CONTACT MEMBER TO GUIDE THE MOVEMENT BETWEEN SAID DISENGAGED AND ENGAGED POSITIONS. 